581
FXUS65 KBOU 050936
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
336 AM MDT MON MAY 5 2025
KEY MESSAGES
- SPRING STORM STARTS TODAY, WITH MAIN PEAK TUESDAY - TUESDAY
NIGHT, WINDS DOWN BY WEDNESDAY. HEAVY FRONT RANGE MOUNTAINS AND
HIGHER FOOTHILLS SNOW ALMOST CERTAIN (80+% CHANCE). SOAKING
RAINS FOR LOWER ELEVATIONS, BUT UNCERTAINTY AS TO HOW MUCH.
- WARMER WEATHER MOVES INTO THE FORECAST AREA ON THURSDAY AND
CONTINUES INTO THE WEEKEND. STILL A FEW LATE DAY SHOWERS AND
STORMS MOST DAYS.
UPDATE
ISSUED AT 336 AM MDT MON MAY 5 2025
MAIN UPDATES IN THE SHORT TERM WERE FOR TIMING THE WAVES OF
PRECIPITATION. THE ONE FOR TODAY LOOKS SLIGHTLY DELAYED, AND
OVERALL IS NOT THAT IMPRESSIVE. THERE SHOULD STILL BE ENOUGH LIFT
IN THE LEFT EXIT REGION OF THE UPPER JET FOR MOST PLACES TO SEE
SHOWERS THIS AFTERNOON WITH A COUPLE EMBEDDED THUNDERSTORMS
(MLCAPE <300 J/KG), BUT QPF AMOUNTS OUTSIDE OF THE MOUNTAINS DON'T
LOOK THAT HIGH. WE'VE GENERALLY GONE WITH THE MODEL AVERAGES WITH
AROUND A TENTH OF AN INCH ON THE PLAINS, AND UPWARDS OF 0.25 TO
0.50 INCH FOR THE MOUNTAINS AND HIGHER FOOTHILLS THROUGH THIS
EVENING. WE THINK THERE WILL THEN BE A FAIR BREAK STARTING THIS
EVENING AND CONTINUING MOST OF THE NIGHT WITH LACK OF FORCING AND
DOWNSLOPE SOUTHERLY FLOW OFF THE PALMER DIVIDE. SPEAKING OF WHICH,
ANOTHER BREEZY/WINDY DAY FOR MOST OF THE PLAINS WITH
SOUTH/SOUTHEAST WINDS GUSTING TO 30-40 MPH.
THE MAIN STORM IS STILL ADVERTISED TO IMPACT OUR FORECAST AREA
STARTING TUESDAY MORNING AND CONTINUING THROUGH TUESDAY NIGHT.
THERE IS VERY GOOD AGREEMENT THAT WE'LL BE GETTING INTO MUCH
STRONGER LIFT AS ANOTHER PIECE OF ENERGY ROTATES OUT FROM THE
UPPER LEVEL LOW AS IT TRACKS NORTHEAST ACROSS NEW MEXICO TUESDAY
AND INTO THE OKLAHOMA PANHANDLE REGION BY TUESDAY NIGHT. WHILE
THERE'S GOOD AGREEMENT ON THIS TRACK, UPSLOPE, AND ADVECTION OF
GULF MOISTURE INTO THE FRONT RANGE, LATENT HEAT RELEASE FROM
CONVECTION IN TEXAS COULD STILL BE A WILDCARD THAT AFFECTS THE
TRACK AND AMOUNT OF SYNOPTIC SCALE LIFT. IT WAS INTERESTING TO
NOTE YESTERDAY'S 12Z ENSEMBLES ALL BEEFED UP QPF NUMBERS FOR THE
FRONT RANGE, WHILE THE MOST RECENT 00Z DROPPED IT A BIT AGAIN. WE
STILL THINK WE'LL HAVE A GOOD SHOT OF 1.25-1.5+" OF RAIN ACROSS
THE I-25 CORRIDOR, AND LOCALLY 2+" LIQUID EQUIVALENT IN THE
FOOTHILLS AND HIGHER EAST FACING SLOPES OF THE FRONT RANGE GIVEN
THE HIGH IVT, DEEP UPSLOPE COMPONENT, AND ANOMALOUSLY HIGH PW.
THAT MEANS HIGH CONFIDENCE WE'LL SEE WINTER STORM CRITERIA HIT IN
THE HIGHER FRONT RANGE MOUNTAINS LIKE THE INDIAN PEAKS, ROCKY
MOUNTAIN NATIONAL PARK, AND I-70 LEADING UP TO THE EISENHOWER
TUNNEL. WE DID SHAVE BACK THE START TIME OF THE WINTER STORM WATCH
TO TUESDAY MORNING, AS TODAY'S SNOW WILL BE MOSTLY AT OR ABOVE
PASS LEVEL WITH CONSIDERABLE MELTING ON HIGHER ELEVATION ROADS
WHERE IT DOES SNOW. THAT WILL CHANGE TOMORROW.
WE ARE ALSO CONCERNED ABOUT POTENTIALLY HEAVIER SNOW IN THE
FOOTHILLS ABOVE 7,500-8,000 FEET TUESDAY AFTERNOON AND NIGHT GIVEN
THE RECENT COOLING IN THE GEFS AND NAM GUIDANCE. HOWEVER, THE EPS
HAS REMAINED FAIRLY STEADY. IN ANY CASE, WE THINK SNOW LEVELS BY
TUESDAY AFTERNOON COULD BE DROPPING TO ~7,500 FEET, AND A LITTLE
LOWER THAN THAT TUESDAY NIGHT. AS A RESULT, WE HAVE COOLED
TEMPERATURES, LOWERED SNOW LEVELS A BIT MORE, AND BEEFED UP SNOW
TOTALS IN THE HIGHER FOOTHILLS WITH MOST PLACES ABOVE 8,000 FEET
EXPECTED TO SEE 8-12" OF SNOW. DESPITE WARM ROAD TEMPERATURES,
TRAVEL IMPACTS WILL ALSO BE POSSIBLE DOWN TO ABOUT THAT LEVEL OR
EVEN LOWER SHOULD SOME OF THE COLDER SOLUTIONS VERIFY, AS HEAVIER
SNOW WITH HIGH LIQUID WATER CONTENT MEANS ROAD TEMPS MAY NOT KEEP
UP WITH MELTING. WE THINK THE FOOTHILLS COULD VERY EASILY END UP
WITH A WINTER WEATHER ADVISORY FOR THIS EVENT TUESDAY THROUGH
TUESDAY NIGHT, WITH SOME POTENTIAL FOR WARNING (30-40%) SHOULD
SOME OF THE HIGHER QPF AND COLDER SOLUTIONS BECOME MORE LIKELY.
NO SIGNIFICANT CHANGES MADE BEYOND WEDNESDAY, WITH GENERALLY
WARMER AND DRIER WEATHER EXPECTED. WE STILL EXPECT ISOLATED TO
SCATTERED LATE DAY SHOWERS AND STORMS, WITH THE HIGHEST COVERAGE
OVER THE MOUNTAINS.
PREVIOUS DISCUSSION THROUGH SUNDAY/
ISSUED AT 213 PM MDT SUN MAY 4 2025
ON MONDAY, ALL THE MODELS SHOW DECENT PRECIPITATION BY AFTERNOON
ACROSS MUCH OF THE CWA, THE MOST AFTER 21Z. THERE IS LIMITED CAPE
PROGGED, MOSTLY OVER THE WESTERN HALF OF THE CWA IN THE AFTERNOON.
SNOW LEVEL ARE STILL PRETTY HIGH MONDAY AFTERNOON; 10,000 FEET AT
THE LOWEST. FOR TEMPERATURES, MONDAY'S HIGHS LOOK ABOUT 10-15
DEGREES COOLER THAN THIS AFTERNOON'S READINGS WITH THE INCREASED
MOISTURE AND CLOUD COVER EXPECTED.
GUIDANCE IS STILL IN GOOD AGREEMENT THAT THE BULK OF THE
PRECIPITATION FROM THIS INCOMING SYSTEM WILL FALL ON TUESDAY AND
TUESDAY NIGHT. HOWEVER, THERE ARE STILL A LOT OF INCONSISTENCIES
BETWEEN MODELS AND MODEL RUNS ON EXACT AMOUNT OF PRECIPITATION AND
PRECIP TYPE.
ENSEMBLE RUNS HAVE NOW HONED IN ON A MORE NORTHERLY TRACK OF THE
SYSTEM, WITH THE UPPER LEVEL CLOSED LOW REACHING NORTHERN NEW MEXICO
BY TUESDAY MORNING. AT THE SURFACE, THERE WILL BE CONSISTENT
SOUTHEASTERLY FLOW ADVECTING AMPLE MOISTURE INTO THE AREA, WITH
WIDESPREAD AND HEAVIER PRECIPITATION THROUGHOUT THE DAY. THE URBAN
CORRIDOR AND EASTERN SLOPES OF THE FRONT RANGE ARE STILL LIKELY TO
RECEIVE THE MOST PRECIPITATION (1-2" OF QPF), DUE TO THIS EVENT
BEING DRIVEN BY UPSLOPE FORCING. HOWEVER, RECENT RUNS HAVE TRENDED
TOWARDS HIGHER AMOUNTS, WITH THE CMCE AND EPS HINTING AT OVER 2" OF
QPF FOR THE HIGH COUNTRY. IN ADDITION, THERE ARE HUGE
INCONSISTENCIES WITH QPF AMOUNTS IN THE PLAINS WITH ENSEMBLE
GUIDANCE RANGING ANYWHERE FROM 0.5-1.5". AT THIS POINT, IT IS TOO
EARLY TO TELL EXACTLY WHERE THE GRADIENT OF MOISTURE WILL DROP OFF
FOR THE PLAINS. HOWEVER, WE ARE CERTAIN THAT THE EASTERN PLAINS WILL
RECEIVE LESS AMOUNTS THAN THE WESTERN PARTS.
IN TERMS OF PRECIPITATION TYPE, CONFIDENCE IS HIGH THAT AREAS ABOVE
9,000 FT. WILL RECEIVE ALMOST A FOOT OF SNOW, WITH THE HIGHEST
ELEVATIONS POSSIBLY SEEING CLOSE TO 2 FT. OF SNOW BY WEDNESDAY
MORNING. BECAUSE OF THIS, WE HAVE ISSUED A WINTER STORM WATCH FOR
THE FRONT RANGE MOUNTAINS MONDAY EVENING THROUGH WEDNESDAY MORNING.
IT IS MORE UNCLEAR IF THE ELEVATIONS BETWEEN 6,500-8,000 FT. WILL BE
DOMINATED BY RAIN OR SNOW, AS MODELS ARE STRUGGLING TO GRASP HOW
COLD TEMPERATURES WILL GET. SOME HIGHER RESOLUTION MODELS INDICATE
THE LOW PRESSURE SYSTEM PULLING IN COLDER 850-MB TEMPS FROM THE
NORTH, WHICH WOULD MEAN MORE SNOWFALL FOR THE FOOTHILLS AND PALMER
DIVIDE. HOWEVER, CONFIDENCE IS NOT HIGH ENOUGH THAT THIS WILL
VERIFY, SO HAVE HELD OFF ON ANY WINTER HIGHLIGHTS FOR THE LOWER
ELEVATIONS FOR NOW.
PRECIPITATION ACROSS THE REGION SHOULD LINGER THROUGH WEDNESDAY AS
THIS SYSTEM TRAVELS EAST. AN UPPER LEVEL RIDGE IS EXPECTED TO START
BUILDING OVER WESTERN UNITED STATES, WHICH WILL BRING ABOVE NORMAL
TEMPERATURES TOWARDS THE END OF THE WEEK AND INTO THE WEEKEND. ASIDE
FROM DAILY CHANCES FOR DIURNAL CONVECTIVE SHOWERS IN THE MOUNTAINS,
DRY CONDITIONS SHOULD PREVAIL.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1132 PM MDT SUN MAY 4 2025
GUSTY WINDS HAVE DECREASED THIS EVENING, BUT ARE EXPECTED TO
INCREASE AGAIN 10Z-14Z AS INVERSIONS WEAKEN SLIGHTLY AS MID LEVEL
CLOUD DECK ROLLS IN. GUSTS TO 20-25 KTS EXPECTED BY THEN. SHOWERS
WILL MOST LIKELY HOLD OFF TIL AFTER 18Z, WITH THE MOST LIKELY
TIME FOR OFF/ON SHOWERS 21Z-24Z, AND THEN A DECREASE AGAIN THIS
EVENING. THE FIRST BATCH OF SHOWERS THIS AFTERNOON IS EXPECTED TO
BE WEAKENING DUE TO THE STRONG SOUTH/SOUTHEAST DOWNSLOPE FLOW
(20G32KTS) OFF THE PALMER DIVIDE. THIS SHOULD ALSO ACT TO KEEP
CEILINGS FROM BOTTOMING OUT DESPITE THE SHOWERS AND STRONG LOW
LEVEL MOISTURE ADVECTION. OVERALL, WE THINK MOSTLY MVFR CONDITIONS
WILL PERSIST 21Z-09Z TUESDAY. AFTER 09Z, WINDS ARE EXPECTED TO
WEAKEN AND TURN MORE EASTERLY WHICH WOULD ALLOW REDUCTIONS IN BOTH
VISIBILITY AND CEILINGS DOWN INTO IFR.
BOU WATCHES/WARNINGS/ADVISORIES
WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR COZ033-034.
UPDATE...BARJENBRUCH
PREVIOUS...RJK/IDEKER
AVIATION...BARJENBRUCH
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